The present invention is directed to a flashbulb having two electrodes fused in gas-tight manner into a glass bulb of hard glass.
As the photographic market evolves flashbulbs are required to have shorter and shorter times for burning and a smaller inside diameter in order to make cameras and flash attachments handier without decreasing the light power and the life span of the flashbulb. Materials previously used for rod-shaped flashbulbs, namely, hard glass for the glass bulb with a cathode of refractory metals having a barium or cesium emitter, place a limit on the energy density. This limit is defined by the following conditions:
the glass wall evaporates in a Xenon arc; PA1 the emitter substances on the cathode surface evaporate; and PA1 the oxidic vapors of the glass wall "poison" the cathode.
Basically, the evaporation processes cannot be prevented since the hot 7000 K. degree plasma of the arc evaporates all solid bodies.